/Engine/Source/Runtime/Slate/Public/Framework/Docking/TabManager.h
Notify the tab manager that the NewForegroundTab was brought to front and the BackgroundedTab was send to the background as a result.
void OnTabForegrounded &40; const TSharedPtr< SDockTab > & NewForegroundTab, const TSharedPtr< SDockTab > & BackgroundedTab &41;